proclaimed Seoul to be its official capital, a position not changed until 1972. Korean War North Korea invaded the South on 25 June 1950, and swiftly overran most of the country. In September 1950 the United Nations force, led by the United States, intervened to defend the South, and advanced into North Korea. As they neared the border with China, Chinese forces intervened on behalf of North Korea, shifting the balance of the war again. Fighting ended on 27 July 1953, with an armistice that approximately restored the original boundaries between North and South Korea. Syngman Rhee refused to sign the armistice, but reluctantly agreed to abide by it. The armistice inaugurated an official ceasefire but did not lead to a peace treaty. It established the Korean Demilitarized Zone (DMZ), a buffer zone between the two sides, that intersected the 38th parallel but did not follow it. North Korea has announced that it will no longer abide by the armistice at least six times, in the years 1994, 1996, 2003, 2006, 2009, and 2013. Large numbers of people were displaced as a result of the war, and many families were divided by the reconstituted border. In 2007 it was estimated that around 750,000 people remained separated from immediate family members, and family reunions have long been a diplomatic priority for the South. Cold War Competition between North and South Korea became key to decision-making on both sides. For example, the construction of the Pyongyang Metro spurred the construction of one in Seoul. In the 1980s, the South Korean government built a 98m tall flagpole in its village of Daeseong-dong in the DMZ. In response, North Korea built a 160m tall flagpole in its nearby village of Kijŏng-dong. Tensions escalated in the late 1960s with a series of low-level armed clashes known as the Korean DMZ Conflict. During this time North and South Korea conducted covert raids on each other in a series of retaliatory strikes, which included assassination attempts on the South and North leaders. On 21 January 1968, North Koreans commandos attacked the South Korean Blue House. On 11 December 1969, a South Korean airliner was hijacked. During preparations for US President Nixon's visit to China in 1972, South Korean President Park Chung-hee initiated covert contact with the North's Kim Il-sung. In August 1971, the first Red Cross talks between North and South Korea were held. Many of the